1. Field of the Invention
The present invention generally relates to a structural material of diamond like carbon (DLC) composite layers and a method of manufacturing the same.
2. Description of Related Art
Diamond like carbon (DLC) thin films have attracted considerable attentions in the last decade, mainly because the DLC thin films have high hardness, high Young's modulus, high abrasive resistance, high thermal conductivity, low friction coefficient, and chemical inertness. By means of property adjustment through such a surface modification, the DLC thin films are applied to various precision work pieces and elements to improve and promote the mechanical performance of the surfaces, and thus the surfaces of the work pieces and products have the special properties similar or close to those of diamond, so as to improve the mechanical performance of the work pieces. The DLC thin films are further applied in severer environment or requirements without reducing the working life, thereby significantly improving the performance of the products and increasing the value of the products.
Although the DLC thin films have excellent properties, during film coating, the surface of the film layer is bombed by coating particles continuously, and thus residual stress is generated inevitably during coating the DLC thin films. Accordingly, excessively high residual stress will cause cracks in the layers, thus decreasing the adhesion of the DLC thin films.
Further, due to the sensitivity of the DLC thin film to environment and the low adhesion caused by the diffusion of interface stress between the DLC thin film and a substrate, the application of the DLC thin film is limited extremely. Therefore, the current technique relates to adding a special intermediate interface layer or adding elements capable of reducing the internal stress of the film into the DLC thin film, so as to improve the structural strength of the DLC thin film and the adhesion between the film and the substrate.
FIG. 1 is a schematic cross-sectional view of a conventional DLC multiple coatings. A Ti layer 102, a TiN layer 104, a TiCN layer 106, a TiC layer 108, and a DLC thin film 110 are coated in sequence on a surface of a substrate 100. In FIG. 1, materials such as Ti/TiN/TiCN are used as the intermediate layers between the substrate 100 and the DLC thin film 110, thus the difference in the lattice constants and thermal expansion coefficients between the substrate 100 and the DLC thin film 110 can be adjusted simultaneously, so as to decrease the internal stress of the film.
However, during coating the DLC thin film, when the ratio of sp3 diamond structure of the manufactured DLC thin film is improved higher, the internal stress of the film is easily increased, thus fragmentation automatically occurs. Additionally, during coating the DLC thin film and compositing with another substrate, due to the high-ratio diamond structure of the film and the poor adhesion between the film and the substrate, film removal likely occurs.